Organinc light emitting display device and method of manufacturing the same

ABSTRACT

An organic light emitting display device and method of manufacturing the same are provided. The organic light emitting display device includes: a thin film transistor (TFT) comprising an active layer, a gate electrode, a source electrode, and a drain electrode; an organic light emitting device including a pixel electrode electrically connected to the TFT and formed of the same material and on a same layer as the gate electrode, an emission layer, and an opposing electrode; and a pad electrode formed of the same material and on same layer as the gate electrode. The pad electrode has openings formed therein.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2010-0105374, filed on Oct. 27, 2010, the disclosureof which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field

Various embodiments of the present invention relate to an organic lightemitting display device and method of manufacturing the same.

2. Description of the Related Art

Flat-panel display devices, such as organic light emitting displaydevices and liquid crystal display devices, are manufactured on asubstrate, on which a thin film transistor (TFT), a capacitor, andwiring are formed. In general, in order to form a fine-structure patternincluding a TFT on the substrate, the pattern is transcribed on an arraysubstrate, using a mask having the fine pattern.

The transcribing of the pattern using the mask generally includes theuse of photo-lithography. During the photo-lithography, a photoresist isuniformly coated on a substrate, the photoresist is exposed using anexposing device such as a stepper (when the photoresist is a positivephotoresist), and the photosensitive photoresist is developed to removeunnecessary portions thereof. After the photoresist is developed, thepattern is etched, using the remaining photoresist as a mask.

A mask including a required pattern is generally prepared prior totranscribing the pattern. Thus, the number of processes performedincreases, thereby increasing manufacturing costs.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide an organic lightemitting display device and a method of manufacturing the same. Thedisplay device has improved adhesion between a pad electrode and aninsulation layer, and thereby, preventing defects during manufacturing

According to various embodiments of the present invention, provided isan organic light emitting display device including: a thin filmtransistor (TFT) including an active layer, a gate electrode, a sourceelectrode, and a drain electrode; and an organic light emitting device.The light emitting device includes a pixel electrode that iselectrically connected to the TFT, which is formed of the same materialand on the same layer as the gate electrode, an intermediate layerincluding an emission layer, and an opposing electrode, which aresequentially stacked. A pad electrode formed of the same material and onthe same layer as the gate electrode is formed on the light emittingdevice and includes openings formed in at least one surface thereof.

According to another exemplary embodiment of the present invention,provided is an organic light emitting display device including: a firstinsulation layer formed on a substrate; an active layer of a thin filmtransistor (TFT) formed on the first insulation layer; a secondinsulation layer formed to cover the active layer; a pixel electrodeformed on the second insulation layer; a lower gate electrode formed onthe active layer; a lower pad electrode formed of the same material andon the same layer as the lower gate electrode; an upper gate electrodeformed on the lower gate electrode; and a upper pad electrode formed onthe lower pad electrode; a third insulation layer formed to cover thepixel electrode, the upper gate electrode, and at least part of theupper pad electrode; and source and drain electrodes contacting thepixel electrode and formed on the third insulation layer. The lower gateelectrode is formed of the same material and on the same layer as thepixel electrode, while being space apart from the pixel electrode. Theupper pad electrode and the lower pad electrode can each include aplurality of electrodes that are spaced apart from each other by apredetermined interval.

According to another aspect of the present invention, there is provideda method of preparing an organic light emitting display device, themethod including: using a first mask to form a thin film transistor(TFT) active layer on a substrate; using a second mask to form a gateelectrode, a pixel electrode, and a pad electrode having a plurality ofopenings, on the active layer; using a third mask to form an interlayerinsulation layer having openings that expose both sides of the activelayer and a part of the electrode pattern; using a fourth mask to formsource and drain electrodes connected to both exposed sides of theactive layer and the pixel electrode; and using a fifth mask to form apixel define layer (PDL) having an aperture that exposes at least partof the pixel electrode.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a plan view schematically illustrating an organic lightemitting display device, according to an exemplary embodiment of thepresent invention'

FIG. 2 is a cross-sectional diagram of the organic light emittingdisplay device of FIG. 1 cut along line II-II of FIG. 1.

FIGS. 3A, 3B, 3C, and 3D are plan views illustrating various forms ofpad electrodes of the organic light emitting display device of FIG. 1.

FIGS. 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13 are cross-sectional diagramsillustrating a method of manufacturing the organic light emittingdisplay device of FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. As those skilled in the art would realize,the described embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification. It will be understood that whenan element such as a layer, film, region, or substrate is referred to asbeing “on” or “connected to” another element, it can be directly on ordirectly connected to the other element, or intervening elements mayalso be present. In contrast, when an element is referred to as being“directly on” or “directly connected to” another element, there are nointervening elements present.

FIG. 1 is a plan view schematically illustrating an organic lightemitting display device 1, according to an exemplary embodiment of thepresent invention. The organic light emitting display device 1 includesa first substrate 10, a thin film transistor (TFT), light emittingpixels, and a second substrate 12 sealed to the first substrate 10.

The TFT, an organic light emitting device (OLED), and a storagecapacitor Cst may be formed on the first substrate 10. The firstsubstrate 10 may be a low-temperature polycrystalline silicon (LTPS)substrate, a glass substrate, a plastic substrate, or a steel usestainless (SUS) substrate.

The second substrate 12 may be a sealing substrate disposed on the firstsubstrate 10, so as to prevent external moisture and/or air frominfiltrating the TFT and light emitting pixels included on the firstsubstrate 10. The second substrate 12 is disposed to face the firstsubstrate 10 and is adhered to the first substrate 10 by a sealingmember 14 disposed along the edges of the first substrate 10 and thesecond substrate 12. The second substrate 12 may be a transparent glassor plastic substrate.

The first substrate 10 includes a display area DA from which light isemitted and a non-display area NDA disposed outside of the display areaDA. According to various embodiments of the present invention, thesealing member 14 is disposed on the non-display area NDA, so as toadhere the first substrate 10 to the second substrate 12.

As described above, the organic light emitting device, the TFT fordriving the organic light emitting device, and wirings electricallyconnected to the organic light emitting device and the TFT, are formedin the display area DA of the first substrate 10. Also, a pad area PA,on which pad electrodes 60 extended from the wirings of the display areaDA are disposed, may be included in the non-display area NDA. The padarea PA includes the pad electrodes 60, which are patterned in apredetermined form.

FIG. 2 is a cross-sectional diagram of the organic light emittingdisplay device 1 of FIG. 1 cut along line II-II of FIG. 1. Referring toFIG. 2, the organic light emitting display device 1 includes a displayarea 101, a channel area 102, a storage area 103, and a pad area 104.

The channel area 102 includes a TFT as a driving element. The TFTincludes an active layer 21, a gate electrode 20, a source electrode 27,and a drain electrode 29. The gate electrode 20 includes a lower gateelectrode 23 and an upper gate electrode 25. The lower gate electrode 23is formed of a transparent conductive material. A gate insulation layer15 is interposed between the gate electrode 20 and the active layer 21,to insulate the gate electrode 20 from the active layer 21. Also, sourceand drain areas 21 a and 21 b, into which a high-concentration ofimpurities is injected, are formed at opposing edges of the active layer21 and are connected to the source and drain electrodes 27 and 29,respectively. Although it is described here that element 27 is thesource electrode and element 29 is the drain electrode, as an ordinarilyskilled artisan understand, alternatively, element 27 may be the drainelectrode and element 29 may be the source electrode.

The display area 101 includes the organic light emitting device (OLED).The organic light emitting device OLED includes a pixel electrode 31connected to one of the source and drain electrodes 27 and 29 of theTFT, an opposing (common) electrode 35, and an intermediate layer 33interposed between the pixel electrode 31 and the opposing electrode 35.The pixel electrode 31 is formed of a transparent conductive material.The pixel electrode 31 and the gate electrode 20 may be formed using asingle process.

The storage area 103 includes a storage capacitor Cst. The storagecapacitor Cst includes a lower capacitor electrode 41 and an uppercapacitor electrode 43. The gate insulation layer 15 is interposedbetween the lower capacitor electrode 41 and the upper capacitorelectrode 43. The upper capacitor electrode 43, the gate electrode 20,and the pixel electrode 31 can be formed using a single process.

The pad area 104 includes the pad electrodes 60. The pad electrodes 60each include a lower pad electrode 63 and an upper pad electrode 65disposed thereon. The lower pad electrode 63 may be formed on the samelayer as the pixel electrode 31, the lower gate electrode 23, and theupper capacitor electrode 43, and may be formed of the same type ofmaterial. Also, the upper pad electrode 65 may be formed on the samelayer as the upper gate electrode 25 and may be formed of the same typeof material.

In a conventional organic light emitting display device, a pixeldefining layer (PDL) (refer to reference numeral 55 of FIG. 2) is formedof an organic material layer and then a spacer (not illustrated) formedof an organic material layer is formed on the PDL. However, when the PDLand the spacer are separately formed, two photolithography processes areneeded. Thus, manufacturing costs and time increase. In this regard, athicker organic layer, referred to as a thick PDL, may be formed tooperate as both the PDL and the spacer. Accordingly, in order to form athick organic layer to a thickness of at least about 3 um, variousattempts have been made to vary the characteristics of organic materialsused to form such an organic layer.

Also, in response to increased demand for larger display devices,attempts have been made to increase size of organic light emittingdisplay devices. As the size of an organic light emitting display deviceincreases, the size of a pad electrode disposed inside the organic lightemitting display device may also be increased.

However, when a thick organic layer (thickness of at least about 3 um)is used in conjunction with a larger pad electrode, stress may begenerated at the interface of the pad electrode and the organic layer.As a result, the organic layer may not be properly coated on the padelectrode, thereby generating panel defects.

In this regard, the organic light emitting display device 1 includesvarious openings formed in the pad electrode 60, so as to increase thecontact area between the pad electrode 60 and an organic layer. Thus,the organic layer may be properly coated on the pad electrode 60.Protrusions may be formed on the surface of the pad electrode 60, so asto minimize the resistance generated between the organic layer and thepad electrode 60. Also, a capillary phenomenon can be used to diffusethe organic layer amongst the protrusions, so as to maximize adhesionbetween the organic layer and the pad electrode 60.

FIGS. 3A through 3D are plan views illustrating various pad electrodes60A, 60B, 60C, and 60D of the organic light emitting display device 1 ofFIG. 1. As illustrated in FIG. 3A, circular or ovoid openings may beuniformly formed on the pad electrode 60A. As illustrated in FIG. 3B,rectangular openings having various sizes may be uniformly formed in thepad electrode 60 b. As illustrated in FIG. 3C, circular or ovoidopenings and rectangular openings, having various sizes, may be formedin the pad electrode 60C. As illustrated in FIG. 3D, the pad electrode60D may include a plurality of electrodes that are spaced apart fromeach other at a predetermined interval.

FIGS. 4 through 13 are cross-sectional diagrams illustrating a method ofmanufacturing the organic light emitting display device 1 of FIG. 1. Asillustrated in FIG. 4, a first insulation layer 13 is formed on thesubstrate 10. More specifically, the substrate 10 may be formed of atransparent glass having SiO₂ as a main component. However, thesubstrate 10 is not limited thereto and may be formed of various othermaterials, such as a transparent plastic or a metal.

The first insulation layer 13 operates as a barrier layer and/or bufferlayer, so as to prevent the diffusion of impurity ions and to block thepermeation of external moisture and air. The first insulation layer 13also operates to planarize the surface of the substrate 10. The firstinsulation layer 13 may include SiO₂ and/or SiN_(x), and may bedeposited by using various deposition methods, such as plasma enhancedchemical vapor deposition (PECVD), atmospheric pressure chemical vapordeposition (APCVD), low pressure chemical vapor deposition (LPCVD), orthe like.

Then, as illustrated in FIG. 5, the active layer 21 of the TFT and thelower capacitor electrode 41 of the storage capacitor Cst are formed onthe first insulation layer 13. More specifically, amorphous silicon isdeposited on the first insulation layer 13 and is then crystallized, soas to form a polycrystalline silicon layer (not illustrated). Theamorphous silicon may be crystallized using various methods, such rapidthermal annealing (RTA), solid-phase crystallization (SPC), excimerlaser annealing (ELA), metal-induced crystallization (MIC),metal-induced lateral crystallization (MILC), sequential lateralsolidification (SLS), or the like. The polycrystalline silicon layer maybe patterned to form the active layer 21 of the TFT and the lowercapacitor electrode 41 of the storage capacitor Cst, using a first mask(not illustrated).

In the current exemplary embodiment of the present invention, the activelayer 21 and the lower capacitor electrode 41 are formed separately.However, the active layer 21 and the lower capacitor electrode 41 may beintegrally formed, as a single body.

Next, as illustrated in FIG. 6, a second insulation layer 15, a firstconductive layer 17, and a second conductive layer 19 are sequentiallydeposited on the substrate 10, on which the active layer 21 and thelower capacitor electrode 41 are formed. The second insulation layer 15may be formed by depositing an inorganic insulation layer, such asSiN_(x) or SiO_(x), using PECVD, APCVD, or LPCVD. The second insulationlayer 15 is interposed between the active layer 21 and the gateelectrode 20 and operates as a gate insulation layer of the TFT. Also,the second insulation layer 15 is interposed between the upper capacitorelectrode 43 and the lower capacitor electrode 41 and operates as adielectric layer of the storage capacitor Cst.

The first conductive layer 17 may include at least one transparentmaterial, such as ITO, IZO, ZnO, and In₂O₃. The first conductive layer17 is patterned to form the pixel electrode 31, the lower gate electrode23, the upper capacitor electrode 43, and the lower pad electrode 63.

The second conductive layer 19 may include at least one materialselected from the group consisting of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd,Ir, Cr, Li, Ca, Mo, Ti, W, MoW, and Al/Cu. The second conductive layer19 is patterned to form the upper gate electrode 25 and the upper padelectrode 65.

Next, as illustrated in FIG. 7, the gate electrode 20, the padelectrodes 60, and electrode patterns 30 and 40 are formed on thesubstrate 10. More specifically, the first conductive layer 17 and thesecond conductive layer 19 are sequentially formed on the substrate 10and are then patterned using a second mask (not illustrated).

Here, the gate electrode 20 is formed on the active layer 21 in thechannel area 102 and includes the lower gate electrode 23, which is apart of the first conductive layer 17, and the upper gate electrode 25,which is a part of the second conductive layer 19. The gate electrode 20is generally positioned at the center of the active layer 21. An n-typeor p-type impurity is doped into the active layer 21 using the gateelectrode 20 as a mask, so as to form the source and drain areas 21 aand 21 b at edges of the active layer 21 (corresponding to both sides ofthe gate electrode 20), and a channel area interposed between the sourceand drain areas 21 a and 21 b.

The electrode pattern 30 is formed in the display area 101, so as toform pixel electrodes. In the storage area 103, the electrode pattern 40is formed on the lower capacitor electrode 41, so as to form the uppercapacitor electrode 43. Also, in the pad area 104, the pad electrodes 60are formed on the second insulation layer 15. The pad electrodes 60 eachinclude the lower pad electrode 63, which is formed from part of thefirst conductive layer 17, and the upper pad electrode 65, which isformed from part of the second conductive layer 19. In the organic lightemitting display device 1, the pad electrodes 60 are patterned to haveopenings, as described above with reference to FIGS. 2 and 3.

As illustrated in FIG. 8, a third insulation layer 50 is deposited onthe substrate 10, on which the gate electrode 20 is formed. The thirdinsulation layer 50 may include at least one organic insulationmaterial, such as, a polyimide, a polyamide, an acryl resin,benzocyclobutene, and a phenol resin. The third insulation layer 50 maybe formed using spin coating. The third insulation layer 50 may bethicker than the second insulation layer 15.

The third insulation layer 50 may alternatively include an organicinsulation material and an inorganic insulation material used in thesecond insulation layer 15. In addition, the third insulation layer 50may alternatively include alternating layers of the organic insulationmaterial and the inorganic insulation material. The third insulationlayer 50 is patterned to form an interlayer insulation layer 51.

As illustrated in FIG. 9, the interlayer insulation layer 51 hasopenings H1, H2, H3, H4, and H5 that expose parts of the electrodepatterns 30 and 40 and the source/drain areas 21 a and 21 b. The thirdinsulation layer 50 is patterned using a third mask (not illustrated),so as to form the openings H1, H2, H3, H4, and H5 and thus, for theinterlayer insulation layer 51.

The openings H1 and H2 partially expose the source/drain areas 21 a and21 b, and the openings H3 and H4 partially expose the second conductivelayer 19 and the first conductive layer 17. The opening H5 partiallyexposes the second conductive layer 19 constituting the upper part ofthe electrode pattern 40.

As illustrated in FIG. 10, a third conductive layer 53 is deposited onthe substrate 10, so as to cover the interlayer insulation layer 51. Thethird conductive layer 53 may include the same conductive material asthe first and second conductive layers 17 and 19. However, the presentinvention is not limited thereto, and the third conductive layer 53 mayinclude various other conductive materials. Also, the conductivematerial is deposited so as to fill the openings H1, H2, H3, H4, and H5.

As illustrated in FIG. 11, the source/drain electrodes 27 and 29, thepixel electrode 31, and the upper capacitor electrode 43 are formed.More specifically, the third conductive layer 53 is patterned using afourth mask (not illustrated) to form the source/drain electrodes 27 and29. Here, one of the source/drain electrodes 27 and 29 (the sourceelectrode 27 in the present exemplary embodiment) is formed, so as to beconnected to the pixel electrode 31 through the opening H3.

After the source/drain electrodes 27 and 29 are formed, the pixelelectrode 31 and the upper capacitor electrode 43 are formed by furtheretching. That is, the portion of the second conductive layer 19 exposedby the opening H4 is removed, so as to form the pixel electrode 31.Then, the portion of the second conductive layer 19 exposed by theopening H5 is removed, so as to form the upper capacitor electrode 43.Accordingly, the pixel electrode 31, the lower gate electrode 23, theupper capacitor electrode 43, and the lower pad electrode 63 are formedfrom portions of the same layer of material.

Then, as illustrated in FIG. 12, an n-type or p-type impurity isinjected through the opening H5, so as to dope the lower capacitorelectrode 41. The impurity may or may not be the same as the impurityused to dope the active layer 21.

As illustrated in FIG. 13, the PDL 55 is formed on the substrate 10.More specifically, a fourth insulation layer 55 is deposited on thesubstrate 10, on which the pixel electrode 31, the source/drainelectrodes 27 and 29, and the upper capacitor electrode 43 are formed.

The fourth insulation layer 55 may include at least one organicinsulation material, such as, a polyimide, a polyamide, an acryl resin,benzocyclobutene, and a phenol resin, and may be formed using spincoating. Also, the fourth insulation layer 55 may include the organicinsulation material and an inorganic insulation material, such as SiO₂,SiN_(x), Al₂O₃, CuO_(x), Tb₄O₇, Y₂O₃, Nb₂O₅, and Pr₂O₃. In addition, thefourth insulation layer 55 may include alternating layers of the organicmaterial and the inorganic material, as recited above with regard tosecond insulation layer 15.

The fourth insulation layer 55 is patterned using a fifth mask (notillustrated). As such, an opening H6 is formed to expose a portion ofthe pixel electrode 31, thereby forming the PDL 55 that defines pixels.

Then, as illustrated in FIG. 2, the intermediate layer 33 and theopposing electrode 35 are formed in the opening H6 and on the pixelelectrode 31. The intermediate layer 33 may have a single-layeredstructure of an emissive layer (EML). The intermediate layer may includeadditional layers, such as, a hole transport layer (HTL), a holeinjection layer (HIL), an electron transport layer (ETL), and anelectron injection layer (EIL).

The intermediate layer 33 may include a low-molecular weight organicmaterial or a polymer organic material. When the intermediate layer 33is formed of the low-molecular weight organic material, the intermediatelayer 33 may include the HTL and HIL adjacent to the pixel electrode 31and may include the ETL and the EIL adjacent to the opposing electrode35. In addition, various layers may be stacked if needed. The organicmaterial used herein may include copper phthalocyanine (CuPc),N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), ortris-8-hydroxyquinoline aluminum (Alq3).

When the intermediate layer 33 is formed of the polymer organicmaterial, the intermediate layer 33 may only include the HTL adjacent tothe pixel electrode 31. The HTL may be formed on the pixel electrode 31through inkjet printing or spin coating usingpoly-(2,4)-ethylene-dihydroxy thiophene (PEDOT) or polyaniline (PANI).The organic material may be a polymer organic material such aspoly-phenylenevinylene (PPV) or polyfluorene. A color pattern may beformed using a general method, such as inkjet printing, spin coating, orlaser thermal transference.

The opposing electrode 35 may be deposited on the substrate 10 and maybe referred to as a common electrode. In the organic light emittingdisplay device 1, the pixel electrode 31 operates as an anode and theopposing electrode 35 operates as a cathode, or vice versa.

When the organic light emitting display device is a bottom emission-typedisplay device, in which an image is projected through the substrate 10,the pixel electrode 31 may be transparent and the opposing electrode 35may be reflective. A reflective electrode may be formed by depositing ametal having a small work function, for example, Ag, Mg, Al, Pt, Pd, Au,Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca, LiF/Al, or compounds thereof, so as tohave a thin thickness.

Although not illustrated, a sealing member (not illustrated) or amoisture absorbent (not illustrated) may be further deposited on theopposing electrode 35, in order to protect the organic light emittinglayer from outside moisture and oxygen. In processes using the masks toform the organic light emitting display device, a stacked layer may beremoved by dry etching or wet etching.

In the bottom emission type display device, a metal layer is separatelyformed from the pixel electrode disposed without a reduction in thenumber of masks, so that light emission efficiency of the pixelelectrode increases, an etching property of the gate electrode issecured, the display quality of the display device increases, processesare simplified, and defects are reduced.

In the above exemplary embodiments, the organic light emitting displaydevice is illustrated. However, the present invention is not limitedthereto, and various display devices, such as a liquid crystal displaydevice, may be used. In the drawings, only one TFT and one capacitor areillustrated for convenience of description. However, the presentinvention is not limited thereto, and a plurality of TFTs and capacitorsmay be included.

According to aspects of the present invention, a manufacturing processmay be simplified, an adhesive strength between the pad electrode andthe insulation is improved, and thus, defects may be prevented.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

What is claimed is:
 1. An organic light emitting display devicecomprising: a thin film transistor (TFT) disposed on a substrate andcomprising an active layer, a gate electrode, a source electrode, and adrain electrode; an organic light emitting device disposed on thesubstrate, comprising a pixel electrode electrically connected to theTFT, an emission layer disposed on the pixel electrode, and an opposingelectrode disposed on the emission layer; and a pad electrode disposedon the substrate and comprising openings formed therein, the openingsbeing through-holes formed in the pad electrode, wherein the pixelelectrode, the gate electrode, and the pad electrode comprise the sametype of material and are formed on a same layer of the display device.2. The organic light emitting display device of claim 1, wherein theopenings are circular or ovoid and are uniformly spaced apart.
 3. Theorganic light emitting display device of claim 1, wherein the openingsare rectangular and are uniformly spaced apart.
 4. The organic lightemitting display device of claim 1, wherein: the gate electrodecomprises a lower gate electrode and a upper gate electrode disposed onthe lower gate electrode; the pad electrode comprises a lower padelectrode and an upper pad electrode disposed on the lower padelectrode; the lower gate electrode and the lower pad electrode areformed of the same material and on the same layer of the display device;and the upper gate electrode and the upper pad electrode are formed ofthe same material and on the same layer of the display device.
 5. Theorganic light emitting display device of claim 4, wherein the lower gateelectrode, the pixel electrode, and the lower pad electrode eachcomprise at least one material selected from the group consisting ofITO, IZO, ZnO, and In₂O₃.
 6. The organic light emitting display deviceof claim 4, wherein the upper gate electrode and the upper pad electrodeeach comprise at least one material selected from the group consistingof Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti, W, MoW, andAl/Cu.
 7. The organic light emitting display device of claim 1, whereinthe pixel electrode is electrically connected to the source electrode orthe drain electrode.
 8. An organic light emitting display devicecomprising: a first insulation layer disposed on a substrate; an activelayer of a thin film transistor (TFT) disposed on the first insulationlayer; a second insulation layer disposed on the active layer; a pixelelectrode disposed on the second insulation layer; a lower gateelectrode disposed on the second insulation layer and facing the activelayer; a lower pad electrode disposed on the second insulation layer; aupper gate electrode disposed on the lower gate electrode; an upper padelectrode disposed on the lower pad electrode; a third insulation layercovering the pixel electrode, the upper gate electrode, and the upperpad electrode; and an electrode of the TFT disposed on the thirdinsulation layer and electrically connected to the pixel electrode,wherein, the upper pad electrode and the lower pad electrode eachcomprise a plurality of electrodes that are regularly spaced apart fromeach other and are all electrically connected to the TFT, the lower padelectrode and the lower gate electrode comprise the same type ofmaterial, the upper pad electrode and the upper gate electrode comprisethe same type of material.
 9. The organic light emitting display deviceof claim 8, wherein the lower gate electrode, the pixel electrode, andthe lower pad electrode each comprise at least one material selectedfrom the group consisting of ITO, IZO, ZnO, and In₂O₃.
 10. The organiclight emitting display device of claim 8, wherein the upper gateelectrode and the upper pad electrode each comprise at least onematerial selected from the group consisting of Ag, Mg, Al, Pt, Pd, Au,Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti, W, MoW, and Al/Cu.
 11. The organic lightemitting display device of claim 1, wherein the pixel electrode, thegate electrode, and the pad electrode each comprise a portion of a firstelectrode layer and an overlapping portion of a second electrode layer.12. The organic light emitting display device of claim 1, wherein theopenings extend completely through the pad electrode.
 13. An organiclight emitting display device comprising: a thin film transistor (TFT)disposed on a substrate and comprising an active layer, a gateelectrode, a source electrode, and a drain electrode; a gate insulationlayer disposed on the substrate and between the gate electrode and theactive layer; an organic light emitting device disposed on thesubstrate, comprising a pixel electrode electrically connected to theTFT, an emission layer disposed on the pixel electrode, and an opposingelectrode disposed on the emission layer; a pad electrode disposed onthe substrate and comprising through-holes formed therein; and aninterlayer insulation layer disposed on the pad electrode, theinterlayer insulation layer extending through the through-holes of thepad electrode to contact the gate insulation layer.